The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
The internal combustion engine, particularly with regard to passenger car and light truck applications, has been the subject of extensive and exhaustive development. One of the more recent improvements involves operation of an internal combustion engine as a flexible fuel engine, i.e., an engine operating on a variety of fuels, most commonly gasoline and E85 (a mixture of 85 percent ethanol and 15 percent gasoline). While a flexible fuel engine presently offers certain advantages from the standpoint of fuel expense and the larger issue of foreign oil dependency, there are operational issues which are the subject of much contemporary research and development.
For example, while a typical flexible fuel engine operating on E85 offers performance improvements due to the higher octane of the ethanol that allows the spark timing to be set at more favorable crank angles under heavy load conditions, these improvements are limited because the engine air flow, which is the primary power limiting factor, remains unchanged. Thus, the performance and fuel economy potential of the E85 fuel are not fully realized.
Another technology undergoing rapid development is referred to as impulse charging. Here, a rapidly operating, essentially two position impulse valve is disposed in each intake runner between the common air supply and the conventional intake valve. Generally speaking, it is disposed proximate the intake valve such that it defines a relatively short length of intake runner which is opened and closed by the impulse valve in timed relation to the operation of the intake valve.
During the first half of the intake stroke, the impulse valve is closed, creating a vacuum. When the impulse valve opens, air is rapidly drawn into the cylinder from the intake manifold. At the end of the intake stroke, the impulse valve rapidly closes to trap a maximum possible amount of air in the intake runner and cylinder downstream of the impulse valve. Air in the runner downstream of the impulse valve is compressed to higher pressures during the first part of the compression stroke while the intake valve is still open. As the intake stroke begins again, this pressurized air enhances scavenging, reduces the in-cylinder temperature and minimizes any pre-ignition tendency. An impulse charged engine typically provides improved volumetric efficiency.
Because of the new and developing nature of these technologies, improvements in flexible fuel and impulse charging technologies are both possible and desirable. The present invention relates to an improvement for an internal combustion engine utilizing these technologies.